Septic Arthritis

How bacteria enter joints

hematogenous spread

direct inoculation/trauma

contiguous spread

Joint Disease Risk

RA, OA, Gout, SLE

Prosthetic Joints, Surgery, Trauma Risk

post joint replacement infections can be hard to treat

Endemic Tick Bite Risk

borrelia

Immunosuppression Risk

DM can predispose to Pseudomonas

HIV/AIDS

IVDU Risk

usually involves sternoclavicular joint

staph aureus

Pseudomonas

Bacteremia Risk

endocarditis

indwelling catheters or IV lines

Age

elderly more at risk

peds at risk for hematogenous spread

Sexually Active Risk

n. gonorrhoeae 

disseminated gonococcal infection

Poor Skin Integrity Risk

chronic skin ulcers

pressure sores

psoriasis as entry point

Clinical Presentation

acute localized onset (prosthetics may be slow)

severe joint pain worse with movement

fever and systemic symptoms

monoarticular (gonorrhea can be polyarticular)

Impacted Joints (most to least)

knee

hip

shoulder

elbow/ankle

Gonococcal Septic Arthritis

migratory polyarthritis

tenosynovitis

pustular rash

Protein A

Staph aureus virulence factor preventing opsonization and phagocytosis

MecA

MRSA virulence factor causing methicillin resistance

Hemolysin

Staph aureus virulence factor punching holes in RBCs, WBCs, chondrocytes

Neisseria Virulence Factors

pili with antigenic variation

IgA protease

Borrelia Virulence Factors

antigenic variation

periplasmic flagella to disseminate

Exotoxin A

Pseudomonas virulence factor

AB toxin prevents protein synthesis and causes cell death

Diagnosis

joint aspiration

blood cultures

imaging may show effusion or soft tissue involvement

Synovial Fluid Findings

high WBCs (>50,000), mainly PMNs

cloudy

low glucose and elevated protein

positive gram stain and culture

Empiric Therapy: no specific risk factors

vancomycin

nafcillin, oxacillin, cefazolin (if low MRSA concern)

Empiric Therapy: Concern for Gram Neg

vancomycin

ceftriaxone, cefepime, piperacillin-tazobactam

Empiric Therapy: Sexually Active Adults

ceftriaxone

+/- doxycline to cover for Chlamydia

Empiric Therapy: Peds

vancomycin

cefotaxome, ceftriaxone

Empiric Therapy: Prosthetics or Surgery

vancomycin

cefepime, ceftazidime, piperacillin-tazobactam

Duration of Targeted Therapy

2-4 weeks IV

2-4 weeks oral

Targeted Therapy: Borrelia

28 days doxycycline

Targeted Therapy: Gonorrhea

IV ceftriaxone, then 7 days doxycycline

Prevention

diagnose and treat early Lyme arthritis

early management of skin infections and bacteremia

prophylactic antibiotics for high risk procedures

sterile and aseptic hospital

avoid high risk behavior